1. Field of the Invention
The present invention relates to an electric power converting apparatus and particularly relates to a vehicular electric power converting apparatus used with a vehicular rotating motor installed in a vehicle such as an automobile.
2. Description of the Related Art
For vehicular rotating motors, a power element is used as a rectifying device so as to achieve higher efficiency. A rectifying method is used by which an electric power converting apparatus reduces losses caused by the rectifying device, the electric power converting apparatus including a power element and a power element driving signal generating unit that generates a signal to drive the power element.
Further, to generate a torque by changing the direction of the current flowing in a power element and to be able to address not only a power-generation process but also a driving process, a controlling method that causes a motor to perform more complicated operations than those realized in commonly-exercised motor control has also been known, the controlling method employing a high-performance microcomputer that has a high computation-processing speed and is able to accommodate a large number of interruptions and timers (see Japanese Patent Application Laid-open No. 2009-284564).
Also, another method has been proposed by which, in the case where the operations of a microcomputer that controls the driving power and the power-generation power of a motor generator are not stable, only minimal power-generation process is maintained, instead of stopping all the functions (see Japanese Patent Application Laid-open No. 2005-137065).
However, for the reason that, for example, high-performance microcomputers include a large-scale memory, it is extremely difficult to obtain a high-performance microcomputer that meets ambient-temperature conditions observed in a position very close to an internal-combustion engine where the vehicular electric power converting apparatus is installed. Thus, a problem arises where the substrate on which the high-performance microcomputer is mounted needs to have a cooling mechanism or needs to be positioned away from the vehicular electric power converting apparatus.
Also, the processing capabilities of microcomputers that meet the ambient-temperature conditions observed in a position very close to an internal-combustion engine where the vehicular electric power converting apparatus is installed are not so high. Thus, there is another problem where the performance levels of those microcomputers are not high enough to realize the operations that are more complicated than those realized in commonly-exercised motor control.
Further, it is necessary to maintain the power-generation process at all times other than when actively causing the motor generator to perform a driving operation. Thus, it is necessary to keep causing electric current of a certain level to flow in the rotor. In the case where a sudden change has occurred in the load (e.g., when the load suddenly becomes small while a power-generation process is being performed with a large load), the power element being used can be destroyed by a sudden rise in the voltage at a power generator terminal.
In the case where a microcomputer is used for monitoring the operation state of the power-generation process described above, a large load is imposed by the processing performed in the microcomputer. A large burden is created by, for example, a process of exercising control so as to turn on and off all the phases of the power element that is connected to a stator, according to the rotation position and the speed of the rotor.
In view of the circumstances described above, it is an object of the present invention to obtain an electric power converting apparatus that is able to improve the reliability level of the power-generation operation control while reducing the load of the processing performed by the microcomputer.